GLEN ELLYN, Ill. — It skipped tolls. It had a Twitter hashtag and a GPS tracker. It even posed for photos with groupies.

The 50-foot-wide, 15-ton electromagnet attracted a sensation wherever it went during its slow, delicate 3,200-mile journey from New York to suburban Chicago. The land-and-sea trip culminated when scientists threw a rock star's welcome for the mysterious, shrink-wrapped cargo on Friday as it arrived at the Fermi National Accelerator Laboratory to help study blazing-fast particles.

"'Oh look, they found a flying saucer!'" retired software developer Chris Otis recalled thinking when he saw the massive, disc-shaped device when it made a pit-stop in a Costco parking lot.

Otis used his cellphone to take photos as he and others marveling the contraption wondered what would happen if it suddenly went live. Electromagnets need an electric current to work.

"I figure somebody at Fermilab is going to plug the damn thing in, turn it on and my watch is going to stop running, everybody's hearing aides are going to sail across the room," Otis said with a laugh. "I have no idea. Turn it on and the Martians will hone in on it."

Fermilab officials plan to use the magnet in a physics experiment called Muon g-2 that will study subatomic particles at their lab in Batavia, outside Chicago. The experiment will study the properties of muons, subatomic particles that live only 2.2 millionths of a second.

The results of the experiment could create new discoveries in the realm of particle physics, said Chris Polly, manager of the Muon g-2 project at Fermilab.

The hulking magnet is a hand-me-down from New York, where it was built in the 1990s with aluminum and steel by scientists at the Brookhaven National Lab on eastern Long Island. It has superconducting coils inside and, at the time it was built, was the largest electromagnet in the world.

Brookhaven scientists no longer had a need for the electromagnet, and shipping it to the Midwest for about $3 million was cheaper than the alternative. Constructing an entirely new electromagnet could have cost as much as $30 million, Polly estimated.

In any case, at least they did not have to pay tolls on the parts of the journey that took it over land.

"We've been assured that we don't have to pay tolls, but we're waiting to see if we get the violation notice in the mail. It'd be pretty hard to dispute," said Fermilab spokesman Andre Salles, who was among the magnet's traveling companions for about 10 days of the trip.

Moving the thing, however, was in some ways as complicated and as delicate a maneuver as building it. It could not be taken apart or twisted more than about an eighth of an inch without irreparably damaging the coils, Polly said.

It started its trip in late June, floating by barge down the East Coast into the Gulf of Mexico — where it outran a tropical depression — then up the Mississippi River, where it was photographed drifting past St. Louis' arch on its way into Illinois.

"We had to hurry up and get going through the Gulf of Mexico and really have the tugboat pour it on," Terry Emmert Jr., vice president of Emmert International, said while recalling the race to avoid the storm. His company moved the magnet across the country.

Earlier in the journey, it spent almost a week docked in Norfolk, Va., because of bad weather, but the team traveling with it found a welcome diversion.

"The port happened to be across the street from a minor league baseball stadium so the barge crew spent the whole week there," Salles said.

Just south of Chicago, it was hauled out of the water and strapped onto a specially made 16-axel flatbed truck for its final leg. It traveled at a mere 5 to 15 mph, with a behemoth bumper sticker informing puzzled onlookers that it was "Driving discovery in particle physics."

It was a night owl that traveled after dark when roads weren't as crowded, staging during the day at a Costco parking lot in suburban Bolingbrook and at a forest preserve.